Post on 05-Apr-2018
The Alea Reactive Dataflow Systemfor GPU Parallelization
Philipp Kramer, Luc BläserInstitute for Software, HSR Rapperswil
Daniel EgloffQuantAlea, Zurich
Funded by Swiss Commission of Technology and Innovation, Project No 16130.2 PFES-ES
HLPGPU 201619 Jan 2016
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GPU Parallelization Is Tough
Massive Parallel Power
Not easy to use
□ Vector parallel and machine-centric programming models
□ Invocation and data management logic
5760 Cores
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Simplify GPU Programming
GPU parallel programming for (almost) everyone
□ No GPU experience required
□ Fast development
□ Good performance
On the basis of .NET
□ Available for C#, F#, VB etc.
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Alea Dataflow Programming Model
Dataflow
□ Graph of operations (pre-fabricated)
□ Data propagated through graph
Reactive
□ Feed input in arbitrary intervals
□ Listen for asynchronous output
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Graph Construction
e.g. Markov-Chain-Step:
var splitter = new Splitter<float[,], float[]>();var mvp = new MatrixVectorProduct<float>();var merger = new Merger<float[,], float[]>();
splitter.First.ConnectTo(mvp.Left);splitter.First.ConnectTo(merger.First);splitter.Second.ConnectTo(mvp.Right);mvp.ConnectTo(merger.Second);
splitter.Second.OnReceive(Console.WriteLine);
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SplitterT[]T[,]
T[,], T[]
Merger
T[]T[,]
T[,], T[]
MatrixVector
Product
T[,] T[]
T[]
Dataflow Execution
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SplitterT[]T[,]
T[,], T[]
Merger
T[]T[,]
T[,], T[]
MatrixVector
Product
T[,] T[]
T[]
SplitterT[]T[,]
T[,], T[]
Merger
T[]T[,]
T[,], T[]
MatrixVector
Product
T[,] T[]
T[]
SplitterT[]T[,]
T[,], T[]
Merger
T[]T[,]
T[,], T[]
MatrixVector
Product
T[,] T[]
T[]
SplitterT[]T[,]
T[,], T[]
Merger
T[]T[,]
T[,], T[]
MatrixVector
Product
T[,] T[]
T[]
M, v
M
M
v
M v'
splitter.Input.Send(new Tuple<>(M, v);
M, v’
Cyclic Graph
Corresponds to iterative calculation
e.g. Markov-Chain steady-state:
Func<int, float[], float[], bool> steadyCondition = …;Func<float[], float[], float[]> aggregation = …;var approx = new Approximator<float[,], float[]>(
steadyCondition, aggregation);
approx.Iterate.ConnectTo(splitter);
merger.ConnectTo(approx.Continue);
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SplitterT[]T[,]
T[,], T[]
MergerT[]T[,]
T[,], T[]
MatrixVector
Product
T[,] T[]
T[]
Approximator
T[,], T[]T[,], T[]
T[,], T[] T[,], T[]
e.g. Monte Carlo Pi
var randoms = new RandomMersenne<float>(0, 1);randoms
.Pairing()
.Map(p => p.Left * p.Left + p.Right * p.Right <= 1 ? 1f : 0f)
.Average()
.OnReceive(x => Console.WriteLine(4 * x));
Fluent Graph Construction
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Random
int
Pairing
Map
Average
float[]
float[]
float[]
float[]
float[]
float[]
float
Runtime System behind the Scenes
Operations implement GPU and/or CPU
Automatic memory copying
□ only when needed
GPU garbage collection
Multi-GPU support
Scheduling with .NET TPL
GPU
CPU
COPY
COPY
COPY
COPY
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GPU Parallelization can be Easy
Pre-fabricated and custom operations□ Vector parallel and machine-centric programming models
Automatic orchestration□ Invocation and data management logic
□ Garbage collection
□ Synchronization
5760 Cores
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Performance Comparison to CUDA C
GPU Kernels written in C# in Cuda C style
Comparison of GPU-kernel-performance to CUDA C
□ GeForce GTX Titan Black (2880 cores)
Benchmark Speedup
Average 1.12
Matrix Convolution 1.03
Matrix AB + BC + CA 0.81
Monte Carlo π 1.06
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Applications and Performance
GeForce GTX Titan Black (2880 cores) vs. CPU (4 Core Intel Xeon E5-2609 2.4GHz)
Option Pricing Case (single GPU, 32 options)
Training Phase of Neural Network Case (MNIST data)
Configuration Speedup
16k paths/it, 30 days 6
32k paths/it, 90 days 18
128k paths/it, 360 days 31
Configuration Unopt. Speedup Opt. Speedup
30 hidden neurons 2.4 3.3
480 hidden neurons 24 33
7680 hidden neurons 93 124
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Conclusions
Simple GPU parallelization in .NET
□ Fast development with generic prefabricated operations
□ Cleaner and slimmer code by separation of concerns
□ Possibility to define custom operations
Efficient runtime system
□ Automatic data movement and GPU garbage collection
□ Low overhead compared to CUDA C
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Further Information
www.quantalea.com
Prof. Dr. Luc BläserHSR Hochschule für Technik RapperswilInstitute for Softwarelblaeser@hsr.chhttp://concurrency.ch
Dr. Daniel EgloffQuantAlea GmbH
Switzerlanddaniel.egloff@quantalea.netwww.quantalea.com
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